A conventional steering apparatus with a steer-by-wire (SBW) system is disclosed in Patent Document 1 listed below. As shown in FIG. 1, this steering apparatus 100 includes: a steering wheel 101 operated by a driver; a steering angle sensor 102 for detecting a steered amount of the steering wheel 101 as an electric signal; a steering mechanism 103 capable of changing a steer angle of road wheels; an SBW control unit 104 for controlling a steering motor 103a of the steering mechanism 103 based on the electric signal detected by the steering angle sensor 102; and an electromagnetic clutch 105 capable of mechanically connecting the steering wheel 101 and the steering mechanism 103.
As shown in FIG. 2, the electromagnetic clutch 105 includes: a first clutch plate 106 rotated in conjunction with steering force onto the steering wheel 101; a second clutch plate 107 connected to an input shaft of the steering mechanism 103 and opposed to the first clutch plate 106; an electromagnetic clutch unit 108 for generating electromagnetic force to urge the first clutch plate 106 in a disconnection direction; and a spring 109 for urging the first clutch plate 106 in a connection direction. Clutch grooves 106a and 107a are formed in a radial pattern on opposed surfaces of the first and second clutch plates 106 and 107, respectively.
In the above-described configuration, the SBW control unit 104 sets the electromagnetic clutch 105 in the disconnected state by energizing an electromagnetic coil 108a in normal time to disconnect a mechanical connection between the steering wheel 101 and the steering mechanism 103. Then, the SBW control unit 104 drives the steering mechanism 103 according to an electric variable detected by the steering angle sensor 102 to steer the road wheels (not shown) when the steering wheel 101 is steered.
When it is determined that the steering motor 103a or the like have failed, the SBW control unit 104 stops the energization to the electromagnetic coil 108a, and switches the electromagnetic clutch 105 from the disconnected state to the connected state and stops controlling the steering mechanism 103 based on the electric variable detected by the steering angle sensor 102. As a result, steering force onto the steering wheel 101 is conducted to the steering mechanism 103 through the electromagnetic clutch 105 and the road wheels (not shown) are steered by the steering mechanism 103.
As described above, in the conventional steering apparatus with the SBW system, it is possible to steer the road wheels by the electromagnetic clutch 105 when the system has failed. In addition, since the clutch grooves 106a and 107a are formed on the opposed surfaces of the first and second clutch plates 106 and 107, large torque can be transmitted. Patent Document 1: Japanese Patent Laid-Open Publication No. 2004-237785